1. Field of the Invention
The present invention relates generally to the fields of tires and tire pressure gauges. More specifically the present invention relates to an air pressure gauge apparatus which is combined with a tire valve stem to remain on the stem and display the tire pressure accurately and reliably over a wide range of ambient temperatures. The pressure gauge apparatus displays the tire pressure either continuously or momentarily with the application of force to a portion of the apparatus, so that the user can see at a glance whether the tire is properly inflated, and thus know at a glance whether the tire is safe and providing optimum tire wear and fuel efficiency. The gauge apparatus preferably is combined with the valve stem either by screwing it onto existing external cap threads of the valve stem and letting it remain attached until momentary removal during tire inflation, or by integrating it permanently into the structure of the valve stem during stem manufacture.
The essential elements of the continuous reading display version of the apparatus include an apparatus housing, containing a received air chamber for placement in fluid communication with received air from within a vehicle tire and containing a biasing air chamber containing a fixed quantity of biasing air, the chambers being sealingly separated from each other by a pressure equilibration structure which includes a pressure indicator element. The pressure equilibration structure moves within the housing to alter the relative volumes of the two chambers and thus to equalize the pressures of the two chambers. The pressure indicator element moves relative to the apparatus housing as the equilibration structure moves to equalize chamber pressures to display a tire pressure reading. The gauge apparatus operates on the principle of continuous re-establishment of pressure equilibrium, where alteration of received air pressure from outside the apparatus, that is, from within the tire, causes movement of the pressure equilibration structure within the housing against the trapped, fixed quantity of biasing air sealed within the biasing air chamber, thereby moving the indicator structure to reveal the pressure reading. The biasing air functions as a fixed standard against which varying tire pressure is measured.
2. Description of the Prior Art
There have long been gauges for measuring the pressure of air contained within vehicle tires. All of these prior gauges have relied on springs to provide biasing against which a pressure reading is taken. A problem with such prior gauges is that the pressure or air within the tire varies significantly at various ambient temperatures, while the resilience of a spring varies only negligibly. As a result, these prior gauges can show that the air pressure in a tire is correct when the tire is at or close to the temperature at which the gauge was calibrated, but also can show that the same quantity of air in the same tire is incorrect at an ambient temperature substantially different from the gauge calibration temperature. Thus a tire on an airliner, for example, may be filled and checked with a gauge in a geographic location which has an ambient temperature matching the gauge calibration temperature, and then the airliner may fly to a location having a very different ambient temperature so that the gauge shows the correct tire pressure to be incorrect. Furthermore, ambient temperature at high altitudes can be close to freezing, so that upon landing the airliner tires are still at this temperature and the gauge gives a misleading reading. In a worse case, the tire is filled and checked with the gauge at a temperature far from calibration temperature so that the pressure appears to be correct, but is not, and the airliner is endangered upon landing. The same problem exists for tires on ground vehicles, such as trucks and automobiles that are driven long distances north and south. Another problem with such prior gauges is that they become inaccurate at ambient pressures other than the ambient pressure at which they are calibrated. In these gauges, the tire air pressure is counterbalanced by the resilience of the spring plus the ambient pressure of the surrounding atmosphere entering the gauge. Ambient pressure varies with altitude, so that the sum of the spring resilience and ambient pressure varies and the reading is altered for the same tire pressure. Yet another problem with such prior gauges is that springs can lose resiliency, can corrode, and can add cost and complexity to the gauges.
These prior, spring biased gauges include Parker, U.S. Pat. No. 4,310,014, issued on Jan. 12, 1982 for a tire pressure indicator integral with a tire stem; Yabor, U.S. Pat. No. 4,901,747, issued on Feb. 20, 1990 for a tire inflation valve with a pressure indicator; Hunt, et al., U.S. Pat. No. 4,924,697, issued on May 15, 1990 for a tire-mounted air pressure gauge assembly; Huang, U.S. Pat. No. 5,014,643, issued on May 14, 1991 for a tire pressure indicator; Rabizadeh, U.S. Pat. No. 5,503,012, issued on Apr. 12, 1996 for a tire pressure monitoring device; Cummings, U.S. Pat. No. 5,569,849, issued on Oct. 29, 1996 for a visual tire cap pressure gauge; Wang, U.S. Pat. No. 5,856,619, issued on Jan. 5, 1999 for a tire pressure indicator; Halcomb, U.S. Pat. No. 5,979,232, issued on Nov. 9, 1999 for a tire pressure indicator carried aboard a wheel; Chi, U.S. Pat. No. 5,886,254, issued on Mar. 23, 1999 for a tire valve pressure-indicating cover utilizing colors to indicate tire pressure.
On the other hand, Wong, U.S. Pat. No. 4,384,543, issued on May 24, 1983, discloses a air release check valve and indicator device which automatically releases air from an over-inflated tire. A critical problem with Wong is that the device is inoperative, for multiple reasons. First, air from within a tire stem bearing against the piston 19 cannot move piston 19 because its pressure is opposed by equivalent air pressure entering the piston cylinder 16 through port 34. Thus the piston will not move no matter what tire air pressure is introduced into the device housing, and the device cannot function either as a pressure relief valve or as a pressure indicator. Nor can Wong receive air from an air line to fill the tire. Air entering Wong would have no way of moving the piston shaft to place its narrower segment within the partition aperture.
None of the displaceable, pressure measuring structures within the known prior art gauges are at equilibrium and at rest prior to installation on a tire. All have set points above atmospheric, unlike the gauge embodiments of the present application. All can become misleadingly inaccurate at ambient temperatures differing significantly from the gauge calibration temperature.
It is thus an object of the present invention to provide a tire gauge apparatus which relies on pressure equilibration rather than on a mechanical spring to produce a tire pressure reading, and thus gives the same accurate reading over a wide range of ambient temperatures because the pressure of air or other gas retained within a gauge biasing gas chamber changes in precise direct proportion to the pressure of air retained within a tire being tested over widely varying ambient chambers.
It is another object of the present invention to provide such a gauge apparatus which is unaffected by variations in ambient pressure and which gives accurate readings at virtually all ambient pressures, and which remains on the tire and produces an accurate and easily visible tire pressure reading.
It is still another object of the present invention to provide such a gauge apparatus which can be integrated into a valve stem during manufacture.
It is yet another object of the present invention to provide such a gauge apparatus which is initially at equilibrium with the atmosphere, is always active, which measures both under- and over-inflation, which can be constructed with a thin pressure responsive membrane with no elastic force constant, and does not rely on preset valves.
It is finally an object of the present invention to provide such a valve stem which is highly economical to manufacture, simple in design, light weight, compact and highly durable.
The present invention accomplishes the above-stated objectives, as well as others, as may be determined by a fair reading and interpretation of the entire specification.
A tire pressure gauge apparatus is provided for securing to a vehicle tire valve stem mounted to a tire valve stem port in a vehicle tire, the valve stem including a tubular stem body containing a valve assembly having a valve opening mechanism, the stem body having a stem connection end fitting sealingly to the tire valve stem port, and having a stem air receiving end, the apparatus including a housing for placement in fluid communication with received air from within the tire contained within the tire valve stem; a structure for opening the valve opening mechanism; and a pressure equilibration structure dividing the housing into a received air chamber and a biasing air chamber and including a pressure indicator element, the pressure equilibration structure and the pressure indicator element being movable relative to the housing, and the pressure indicator element displaying a pressure reading of received air from within the tire which varies with the position of the pressure equilibration structure relative to the housing; so that alteration of the pressure of received air within the received air chamber from the valve stem causes movement of the equilibration structure within the housing to re-establish pressure equilibrium between biasing air sealed within the biasing air chamber and received air within the received air chamber, and movement of the equilibration structure causes the indicator element to move relative to the housing to provide a received air pressure reading.
A tire pressure gauge apparatus is further provided for securing to a vehicle tire valve stem mounted to a valve stem port in a vehicle tire, the valve stem including a tubular stem body containing a valve assembly having an outwardly biased valve opening shaft, the stem body having a stem connection end with a circumferential groove for fitting sealingly into an edge of the tire valve stem port, and having a stem air receiving end having external threads for affixation of a valve stem cap and having internal threads into which the valve assembly is screwed, the apparatus including a housing for placement in fluid communication with received air from within the tire contained within the tire valve stem; a structure for depressing the valve opening shaft and thereby opening the valve assembly, the structure for depressing being connected to the housing; and a pressure equilibration structure dividing the housing into a received air chamber and a biasing air chamber and including a pressure indicator element, the pressure equilibration structure and the pressure indicator element being movable relative to the housing, and the pressure indicator element displaying a pressure reading of received air from within the tire which varies with the position of the pressure equilibration structure relative to the housing; so that alteration of the pressure of received air within the received air chamber from the valve stem causes movement of the equilibration structure within the housing to re-establish pressure equilibrium between biasing air sealed within the biasing air chamber and received air within the received air chamber, and movement of the equilibration structure causes the indicator element to move relative to the housing to provide a received air pressure reading. The housing preferably is a tubular housing having an open connection end and a closed indicator display end, the biasing air chamber including an indicator display window and terminating in an integral housing end wall; and the pressure equilibration structure preferably includes a diaphragm disk and the indicator element includes an indicator cylinder marked with calibrations and secured to the diaphragm disk and extending into the biasing air chamber and passing adjacent to the indicator display window, the diaphragm disk being sized in diameter to fit within the housing and being sealingly and circumferentially joined to the inner surface of the housing; structure for sealingly securing the diaphragm disk to the step; a valve opening shaft depression structure for depressing the valve opening shaft to release air from within the tire into the received air chamber; structure for securing the valve stem body to and in fluid communication with the received air chamber; so that the apparatus is screwed onto the stem air receiving end to create a seal between the received air chamber and the valve stem body, and so that the valve opening shaft depression structure depresses the valve opening shaft to an extent which opens the valve assembly to pass air from within the tire into the received air chamber and against the diaphragm disk; and so that pressure of received air from within the tire deflects the diaphragm disk toward the biasing air chamber, thereby compressing the biasing air until the pressure of the biasing air rises to equal the pressure of the received air within the received air chamber, whereupon the attached indicator cylinder comes to rest to indicate the pressure of air contained within the received air chamber and within the tire. The calibrations preferably are either circumferential color bands or are lines labeled with pressure reading figures.
The housing once again is preferably a tubular housing having an open connection end and a closed indicator display end, the biasing air chamber including an indicator display window and an integral housing end wall; and the indicator element preferably includes an indicator cylinder dividing the biasing air chamber from the received air chamber and being slidably mounted within the housing to slide into and out of the biasing air chamber, the indicator cylinder being marked with calibrations and passing adjacent to the indicator display window; a valve opening shaft depression structure for depressing the valve opening shaft to release air from within the tire into the received air chamber; structure for securing the valve stem body to and in fluid communication with the received air chamber; so that the apparatus is screwed onto the stem air receiving end to create a seal between the received air chamber and the valve stem body, and so that the valve opening shaft depression structure depresses the valve opening shaft to an extent which opens the valve assembly to pass air from within the tire into the received air chamber and against the indicator cylinder; and so that pressure of received air from within the tire slides the indicator cylinder into the biasing air chamber, thereby compressing the biasing air until the pressure of the biasing air within the biasing air chamber rises to equal the pressure of the received air within the received air chamber, whereupon the indicator cylinder comes to rest to indicate the pressure of air contained within the received air chamber and within the tire.
The housing once again is preferably a tubular housing having an open connection end and a closed indicator display end, the biasing air chamber including an indicator display window and terminating in an integral housing end wall; and the pressure equilibration structure preferably includes a partition wall having a partition wall air passing port and an indicator bellows secured to the partition wall over the partition wall air passing port and extending into the biasing air chamber, the indicator bellows being axially expandable into the biasing air chamber, the indicator bellows being marked with calibrations and passing adjacent to the indicator display window; a valve opening shaft depression structure for depressing the valve opening shaft to release air from within the tire into the received air chamber and into the indicator bellows; structure for securing the valve stem body to and in fluid communication with the received air chamber; so that the apparatus is screwed onto the stem air receiving end to create a seal between the received air chamber and the valve stem body, and such that the valve opening shaft depression structure depresses the valve opening shaft to an extent which opens the valve assembly to pass air from within the tire into the received air chamber and into the indicator bellows; and so that pressure of received air from within the tire expands the indicator bellows into the biasing air chamber, thereby compressing the biasing air until the pressure of the biasing air within the biasing air chamber rises to equal the pressure of the received air within the received air chamber, whereupon the attached indicator bellows ceases to expand, and indicates the pressure of air contained within the received air chamber and tire.
A tire pressure gauge and valve stem apparatus is provided for securing into a valve stem port in a vehicle tire, including a vehicle tire valve stem having a tubular stem body containing a valve assembly, the stem body having a stem connection end with a structure for fitting sealingly into a tire valve stem port, and having a stem air receiving end; a gauge housing secured to the valve stem body in fluid communication with received air contained within the valve stem body through a valve stem body lateral opening; and a pressure equilibration structure dividing the housing into a received air chamber and a biasing air chamber and including a pressure indicator element, the pressure equilibration structure and pressure indicator element being movable relative to the housing and displaying a pressure reading of received air from within the tire which varies with the position of the pressure equilibration structure relative to the housing; so that alteration of the pressure of received air within the received air chamber causes movement of the pressure equilibration structure within the housing to re-establish pressure equilibrium between biasing air sealed within the biasing air chamber and received air within the received air chamber, and movement of the equilibration structure causes the indicator element to move relative to the housing to provide a received air pressure reading. The housing is preferably a tubular housing having a connection end secured to a side of the valve stem body and a closed indicator display end, the biasing air chamber including an indicator display window and terminating in an integral housing end wall; and the pressure equilibration structure preferably includes a diaphragm disk and the indicator element preferably includes an indicator cylinder marked with calibrations and secured to the diaphragm disk and extending into the biasing air chamber and passing adjacent to the indicator display window, the diaphragm disk being sized in diameter to fit within the housing and being sealingly and circumferentially joined to the inner surface of the housing; and structure for sealingly securing the diaphragm disk to the step; so that pressure of received air from within the tire deflects the diaphragm disk toward the biasing air chamber, thereby compressing the biasing air until the pressure of the biasing air within the biasing air chamber rises to equal the pressure of the received air within the received air chamber, whereupon the attached indicator cylinder comes to rest to indicate the pressure of air contained within the received air chamber and within the tire. The calibrations once again preferably are either circumferential color bands or are lines labeled with pressure reading figures.
The housing once again is preferably a tubular housing having a connection end secured to a side of the valve stem body and a closed indicator display end, the biasing air chamber including an indicator display window and terminating in an integral housing end wall; and the indicator element preferably includes an indicator cylinder dividing the biasing air chamber from the received air chamber and being slidably mounted within the housing to slide into and out of the biasing air chamber, the indicator cylinder being marked with calibrations and passing adjacent to the indicator display window; so that pressure of received air from within the tire slides the indicator cylinder into the biasing air chamber, thereby compressing the biasing air until the pressure of the biasing air within the biasing air chamber rises to equal the pressure of the received air within the received air chamber, whereupon the indicator cylinder comes to rest to indicate the pressure of air contained within the received air chamber and within the tire. Once again, the calibrations preferably are either circumferential color bands or are lines labeled with pressure reading figures.
The housing once again is preferably a tubular housing having a connection end and a closed indicator display end, the biasing air chamber including an indicator display window and terminating in an integral housing end wall; and the pressure equilibration structure preferably includes a partition wall having a partition wall air passing port and an indicator bellows secured to the partition wall over the partition wall air passing port and extending into the biasing air chamber, the indicator bellows being axially expandable into the biasing air chamber, the indicator bellows being marked with calibrations and passing adjacent to the indicator display window; so that pressure of received air from within the tire expands the indicator bellows into the biasing air chamber, thereby compressing the biasing air until the pressure of the biasing air within the biasing air chamber rises to equal the pressure of the received air within the received air chamber, whereupon the attached indicator bellows ceases to expand and achieves a substantially fixed position relative to the housing to indicate the pressure of air contained within the received air chamber and within the tire. The tubular housing optionally includes an abrupt reduction in diameter between the connection end and the indicator display end defining a housing step forming a housing shoulder, so that the housing connection end is a wider housing tube segment defining the received air chamber and the housing indicator display end is a narrower housing tube segment defining the biasing air chamber; and the diaphragm disk is secured sealingly against the housing shoulder.
A tire pressure gauge and valve stem apparatus is further provided for securing into a valve stem port in a vehicle tire, including a vehicle tire valve stem having a tubular stem body containing a valve assembly, the stem body having an outer surface and having a stem connection end with structure for fitting sealingly into a tire valve stem port, and having a stem air receiving end; a gauge housing including a housing circumferential wall formed of a translucent material and bowed outwardly from the circumferential wall along the longitudinal axis of the housing circumferential wall and wrapped sealingly and circumferentially around the valve stem body; and the equilibration structure preferably is an elastic bladder contained within the housing circumferential wall and wrapped circumferentially around and sealingly secured to the outer surface of the tubular stem body; a stem branch passageway extending laterally from the interior of the stem body and opening within the bladder; and a substantially opaque liquid contained within an annular space defined between the bladder and the housing circumferential wall together with a certain quantity of biasing air; the quantity and pressure of the biasing air and as the elastic resistance of the bladder in relation to the minimum adequate tire air pressure being so that a tire air pressure of at least a certain magnitude which is deemed adequate causes the bladder to expand radially, to compress the biasing air and to displace the substantially opaque liquid and bear against the inner surface of the housing circumferential wall, making a portion of the bladder visible through the housing circumferential wall, and so that a tire air pressure of less than the certain magnitude deemed adequate permits the elasticity of the bladder and the pressure of the biasing air to retract the bladder from contact with the housing circumferential wall and the substantially opaque liquid to flow between the bladder and the circumferential wall to obscure the bladder from view. The bladder preferably is brightly pigmented and the opaque liquid is darkly pigmented for increased visual contrast between the bladder and the opaque liquid for greater bladder visibility when the bladder bears against the housing circumferential wall.